Topic 5 - on the wild side, biology A2, edexcel snab unit 4

ON THE WILD SIDEPHOTOSYNTHESISProducers (autotrophs) make their own food by photosynthesis6CO2 + 6H20 602 + CH12O6(in the presence of light and chlorophyll)Photolysis is used, the process of splitting water using light energyPhotosynthesis stores energy as glucoseCHLOROPLASTSPhotosynthesis occurs in the chloroplasts (small, flattened organelles). Thylakoid membranes: A system of interconnected, flattened fluid filled sacs. Proteins including photosynthetic pigments and electron carriers are in the membrane and are involved in the light-dependent reaction Granum: A stack of thylakoids Thylakoid space: Fluid within the thylakoid sacs contain enzymes for photosynthesis Stroma: Fluid surrounding the thylakoid membranes. Contains enzymes needed for the light-independent reactions Starch grain: Stores the products of photosynthesisLIGHT DEPENDENT REACTIONSIn the thylakoid membraneADP + Phosphate ATPProduce reduced NADP, ATP and waste oxygen 1) Light energy provided by sun 2) Light absorbed by chlorophyll pigment in chloroplasts 3) Light energy excites electrons in the chlorophyll so they get boosted up to a higher energy level 4) Electrons are accepted and pass along protein carriers in an electron transport chain 5) Energy released from oxidation and reduction of carriers enables ATP to form ADP and a phosphate (photophosphorylation). 6) Electrons and hydrogen ions from the water move along carriers and are accepted by the coenzyme NADP. NADP becomes reduced NADP (NADPH) through photolysis.

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As well as two hydrogen ions being taken from the water, two electrons are taken to replace those from the chlorophyll. The electron transport chain splits water (photolysis) using energy from sunlight. 8) The oxygen from the water is released through the leaf (waste product).…read more

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Chlorophyll a excited and promotes electron to higher energy level e- picked up by electron carrier Enough energy released to photophosphorylate Electrons aren't passed on to NADP, but are passed back into photosystem I via electron carriers ­ electrons repeatedly flow through PSI (recycled).…read more

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Photolysis: Splitting of a molecule using light Hydrolysis: Splitting of a molecule using water (ATP hydrolysed to ADP) Redox reactions: Involve oxidation (losing electrons) and reduction (gaining electrons)Chloroplasts are adapted for photosynthesis because thylakoids have a large surface area somore light can be absorbed. Stroma contains the enzymes needed for light independentreactions and the chloroplast envelops keeps reactants close to reaction sites.…read more

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Parasitism ­ diseased animals will be weakened and not reproduce successfully. They cannot hunt well and are more likely to be caught. Parasites can wipe out whole populations and spread fast when there is a high population (close proximity). Competition for resources GrazingAnthropogenic factors arise from human activity and can be both abiotic and biotic.…read more

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NPP (Net Primary Productivity) is the rate that organic molecules are made into newbiomass.…read more

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Other factors of climate change are: Degree of reflection from ice and snow Extent of cloud cover Changes in sun's radiationExtrapolation = extending a line on a graph ­ we assume there is enough data to establishthe trend accurately and present trends continue. Extrapolation is often the basis forpredictions.…read more

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Biofuels ­ fuels directly from biomass which are burnt to release energy, producing carbon dioxide. Because the amount of carbon dioxide released when burnt is the same removed by photosynthesis, plants are carbon neutral so have no net increase. Plants can be grown all the time so are a renewable energy source. Examples are wood, straw and vegetable oil. They can reduce the use of limited fossil fuels, reducing carbon emissions.…read more

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Hybrid inviability: Hybrids produced but don't live long enough to reproduce Hybrid sterilisation: Hybrid survives long enough to breed but is infertileVALIDATING SCIENCEIn order to test theories, data needs to be collected to prove or disprove it. Scientistswithin the scientific community accept evolution as there is evidence to make it reliable andvalid.Scientists validate data in 3 ways: 1) Scientific journals ­ scientists publish articles describing their work ­ share ideas, theories, experiments, evidence and conclusions.…read more